In order to create various light effects and mood lighting in connection with concerts, live shows, TV shows, sport events or as a part of an architectural installation light fixtures creating various effects are getting more and more used in the entertainment industry. Typically entertainment light fixtures creates a light beam having a beam width and a divergence and can for instance be wash/flood fixtures creating a relatively wide light beam with a uniform light distribution or it can be profile fixtures adapted to project image onto a target surface.
Light emitting diodes (LED) are, due to their relatively high efficiency and/or low energy consumption, long lifetime, and capability of electronic dimming, becoming more and more used in connection with lighting applications. LEDs are used in lighting applications for general illumination such as wash/flood lights illuminating a wide area or for generating wide light beams e.g. for the entertainment industry and/or architectural installations. For instance like in products such as MAC 101™, MAC 301™, MAC 401™, MAC Aura™, MAC Quantum™ Wash, Stagebar2™, Easypix™, Extube™, Tripix™, Exterior 400™ series provided by the applicant, Martin Professional. Further LEDs are also being integrated into projecting systems where an image is created and projected towards a target surface. For instance like in the product MAC 350 Entrour™ provided by the applicant, Martin Professional.
The lifetime and performance of the LEDs depends on the operating temperature of the LED and both lifetime and performance drops dramatically with increasing operating temperature. One of the challenges when cooling LED are the fact that critical temperature of the LEDs in relation the temperature of the surroundings are relatively small (40-70 degrees) and the cooling effect of using ambivalent air is thus not very high. Further when providing projecting LED devices where the light is focused through an optical gate with an imaging object the LEDs are arranged very close together and generates thus much heat in a small area. Several prior art cooling systems have tried to solve this issue, however none of these have yet be found good enough when arranging a significant amount (+20) of LED close together in an array.
WO10069327A1 discloses a moving head light fixture, which moving head light fixture comprises a light generating head, which head is carried in a yoke, which head is rotatable to the yoke, which yoke is rotatable to a base, which head comprises at least one electronic circuit for LED control, where the moving head comprises a first cooling plate comprising a number of LEDs; a second cooling plate comprising said at least one electronic circuit for LED control; and an air flow passage running from at least one end of said moving head, through at least said first cooling plate and/or said second cooling plate and between said first cooling plate and said second cooling plate. The length of the cooling module according to WO20069327 is relatively large, as the electronic circuits for LED control are arranged a distance behind the LEDs in order to provide a flow channel there between. This is not desired in connection with projecting devices where the light is coupled through an optical gate, as the optical systems of such devices are long in order to provide good optical system. The length of head in a moving head light fixture is of the limited due to physical limitations/specifications and it is thus desired to provide a shorter cooling module.
WO11076219A1 discloses a illumination device comprising a number of light sources and a number light collecting means, where the light collecting means collect light generated by the first light sources and convert the light into a source light beam propagating primarily along a primary optical axis. The light source module comprises a cooling module comprising a number of interconnected plane mounting surfaces angled in relation to each other and where the light sources is arranged on said plane mounting surfaces. The cooling module comprises a first side comprising the mounting surfaces and a second side comprising a number of cooling fins defining a number of radial air channels. The length of the cooling module according to WO11076219 is relatively large, as the fan must be arranged at the center part of the cooling module. Further such cooling module is difficult to provide in light fixtures comprising a large number (+20) of LEDs as individual mounting surfaces must then be provided.
WO12167798A1 discloses an illumination device where a number of light sources are arranged on a heat sink and adapted to emit light in substantially the same direction. The heat sink comprises a first cooling plate and a second cooling plate and a first part of the light sources are arrange on the first cooling plate and a second part of the light sources are arranged on the second cooling plate. The first and second cooling plates are further separated by a distance and a flow channel is defined there between. The flow channel allows cooling fluid to flow between the first cooling plate and the second cooling plate whereby the light sources can be cooled by the cooling fluid. The heat sink comprises further a number of light passages allowing light to propagate from the second cooling plate, towards the first cooling plate and through the first cooling plate. WO12167798A1 relates also to a method of cooling light sources emitting light in substantially the same direction. The length of the cooling module according to WO12167798A1 is relatively large, as the LEDs are arranged at two separate PCBs where between a cooling channels is provided.